An effective immune response begins when an antigen or mitogen triggers the activation of T cells. In the process of T cell activation, numerous cellular changes occur, which include the expression of cytokines and cytokine receptors. One of the cytokines involved in the immune response is interleukin-15 (IL-15). IL-15 is a T cell growth factor that stimulates the proliferation and differentiation of B cells, T cells, natural killer (NK) cells, and lymphocyte-activated killer (LAK) cells in vitro. In vivo, the proliferation of these cell types enhances the immune response.
IL-15 binds to a heterotrimeric receptor that consists of the IL-2R.beta. subunit, the IL-2R.gamma. subunit, and a unique IL-15R.alpha. subunit.
Patients benefit from suppression of the immune response in a number of circumstances, for example, in the event of organ transplantation or autoimmune disease. In other circumstances, for example when select immune cells have become malignant or autoaggressive, it is beneficial to actively destroy them.